1. Field of the Invention
The present invention relates generally to coaxial cable end connectors of the type employed in the cable television industry. More particularly, the present invention relates to an inexpensive connector that can be securely fitted to coaxial cables of several different sizes.
2. Description of Related Art
A conventional coaxial cable typically is comprised of a centrally located inner electrical conductor surrounded by and spaced inwardly from an outer cylindrical electrical conductor. The inner and outer conductors are separated by a dielectric insulating sleeve, and the outer conductor is encased within a protective dielectric jacket. The outer conductor can comprise a sheath of fine braided metallic strands, a metallic foil, or multiple layer combinations of either or both.
In the transmission of cable television signals, a large low-loss high capacity coaxial cable is run between utility poles or buried underground, typically along a highway or other thoroughfare. Smaller “drop” cables are connected to this main cable and run to the customer sites, i.e. businesses, residences, schools, etc.
In order to connect a coaxial cable to a port of a device (such as a television, a video recording device, or a cable junction/receiving box within a residence) to receive a transmitted signal, a connector fitting must be installed on the end of the cable. Generally, coaxial cable connectors are provided in two configurations: crimp connectors and compression connectors.
Crimp connectors are generally the lowest cost connectors, and are often used within residences by homeowners to terminate coaxial cables and connect them to their entertainment devices. A typical crimp connector is comprised of three parts: a threaded fastener for securing the connector to an equipment port such as a radio frequency (RF) port, a thin-walled crimpable connector body, and a tubular post contained within the connector body. To terminate and connect the coaxial cable to the crimp connector, the end of the cable is prepared (as will be described subsequently herein), and inserted into the connector. The wall of the connector is then crimped with a crimping tool that has jaws which radially inwardly deform the connector body against the cable end, thereby binding it within the connector.
In contrast, a typical coaxial compression connector for connection to a coaxial cable typically includes four parts: a threaded fastener for securing the connector to the equipment port, a connector body, a tubular post contained within the connector body, and a compression or locking sleeve, which is secured to the connector body and the coaxial cable disposed therein by axial compression against the connector body.
By way of illustration, U.S. Pat. No. 4,902,246 of Samchisen, the disclosure of which is incorporated herein by reference, describes a “snap-n-seal” connector including a connector body, an annular compression sleeve, and optionally, a sealing nut. The connector body includes an annular collar member which peripherally engages the jacket of a coaxial cable, a post member coaxially disposed within the annular collar member to engage the dielectric insulation and the braided shield of the coaxial cable, and a rotatable nut member disposed in combination with the collar and post members. The compression sleeve is configured for snap fitting engagement between the jacket of the coaxial cable and the annular collar member to provide a moisture proof circular seal therebetween and to force the braided shield into mechanical and electrical engagement with the contact spring member an/or the post member. The compression sleeve includes a sealing member to provide a 360 degree moisture proof seal between the compression sleeve and the collar member. The sealing nut includes a sealing member and is threaded onto an interface connector to provide a moisture proof seal between the interface connector and the nut member.
Additionally, U. S. Pat. No. 5,470,257 to Szegda, which is assigned to the assignee of the present invention and incorporated herein by reference, discloses a compression type coaxial cable end connector (known commercially as a “CMP” connector) comprising a connector body having a tubular inner post extending from a front end to a rear end, and including an outer collar surrounding and fixed relative to the inner post at a location disposed rearwardly of the front post end. The outer collar cooperates with the inner post to define an annular chamber with a rear opening. A fastener at the front end of the inner post serves to attach the end connector to a system component. A tubular locking member protrudes axially into the annular chamber through its rear opening.
Compression-type cable connectors are significantly more expensive than crimp type connectors, and also require a more complex corresponding compression tool. Although compression connectors provide a connection with a higher quality signal and greater moisture resistance, they are generally not used by homeowners due the their higher cost. It would therefore be desirable to somehow provide a way to inexpensively transform a crimp connector into a compression connector that utilizes a standard compression tool.
Crimp type cable connectors presently require crimp tools that feature crimping nests for each cable size/construction within a given cable standard such as RG59 or RG6. This often presents problems for inexperienced installers (such as homeowners) in terms of consistent quality of termination.
For compression-type cable connectors, the problem of variation in cable size must also be addressed. In most prior art connectors comprised of a compression sleeve that is fitted to a connector body, the compression sleeve is provided in at least two, and possibly three different sizes to correspond to the three different cable diameters. This is because the compression ring or ferrule of the compression sleeve does not undergo a sufficient reduction in inner diameter during the compression of the sleeve into the connector body when installing the connector on the cable, such that the compression sleeve sufficiently seals and binds to the cable, regardless of its diameter and shield construction.
In addition to carrying two or three different sizes of compression sleeve, a cable technician typically carries a single compression tool. This is inconvenient for the technician, and the process has considerable opportunities for errors in the field that result in improper cable fitting installation and/or loss of compression sleeves and compression tools. For an inexperienced user such as a homeowner, who wants to use inexpensive cable connectors and have minimal tooling costs, this scenario is unworkable. What is needed is an inexpensive way to transform a crimp connector into a compression connector that utilizes a standard compression tool.
A coaxial cable connector is provided as described in U.S. Pat. No. 6,848,939 to Sterling, the disclosure of which is incorporated herein by reference. The coaxial cable connector of Sterling is comprised of an internal body and an external body or bushing (i.e. compression piece) which are assembled together, and which can be activated to clamp upon and seal to an inserted coaxial cable without disassembling the external body from the internal body. The bushing is made of a rigid material such as brass, but includes a deformable inner collar of a plastic such as Delring® that permits the connector to be attached and sealed to cables of varying thickness.
Another connector that functions in a similar manner is described in U.S. Pat. No. 5,879,191 of Burris, the disclosure of which is incorporated herein by reference. Burris describes a cable connector comprising a tubular post and fastening nut, along with a modified form of body member. The body member outer wall includes a series of annular ridges, and the end of the body member includes a beveled surface. The connector includes a collar assembly (i.e. compression piece) that incorporates a gripping ring. The collar assembly has a central passage for receiving the end of the coaxial cable. One end of the collar assembly has an internal bore of a diameter commensurate with the outer diameter of the body member; the internal bore also has annular ridges formed thereon which frictionally engage the ridges on the outer wall of the body member. A compression tool longitudinally compresses the collar assembly over the body member during installation, causing the beveled surface of the body member to cam the gripping ring inwardly toward the tubular post, securing the outer jacket and conductive braid of the coaxial cable therebetween.
Although the connectors of Sterling and Burris are compression connectors, they do not accomplish their results at a low cost. The Sterling and Burris connectors are both configured such that their respective fasteners, tubular posts, and connector bodies are designed to match with their respective compression pieces. Both connectors have the relatively high complexity and the high cost of typical compression cable connectors.
Thus there remains a need for a coaxial cable connector having the locking and sealing advantages of a compression type connector, at about the same low cost as a crimp-type connector. The connector should have a compression piece that can be installed with a simple compression tool.